1. Field of the Invention
The present invention relates to a fixed-focus imaging lens that forms an optical image of a subject on an image sensor, such as, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and an imaging device equipped with the imaging lens and performs imaging, such as a digital still camera, a camera equipped portable phone, a personal digital assistance (PDA), a smartphone, a tablet terminal, a portable game machine, or the like.
2. Description of the Related Art
Along with a widespread use of personal computers in homes, digital still cameras that can input image information, such as imaged landscapes and portraits, in personal computers are spreading rapidly. In addition, more and more portable phones, smartphones, and tablet terminals are equipped with camera modules for image input. Such devices having imaging capabilities use image sensors, such as CCDs, CMOSs, and the like. Recently, as downsizing of these image sensors have advanced, imaging devices as a whole and imaging lenses equipped therein are also demanded to be downsized. At the same time, higher pixel counts of image sensors are also in progress, and high resolution and high performance are demanded for imaging lenses. For example, performance that meets the requirement of higher pixel counts of 5 mega pixels or greater, more preferably, 8 mega pixels or greater are demanded.
In order to meet such demands, an imaging lens composed of a relatively large number of lenses, i.e., five lenses, is proposed. For example, U.S. Patent Application Publication No. 20130093942, U.S. Pat. No. 8,179,614, U.S. Patent Application Publication No. 20130050847, U.S. Patent Application Publication No. 20130077181 and Chinese Patent Publication No. 103018887, each proposes a five element imaging lens, composed of a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a negative refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power, disposed in order from the object side.